Electrically energized toy racing cars are known which may be raced against one another. It is usual in the prior art to provide a track with side walls, or slots, and for the cars to be controlled so that they are directed along the slots, or so that they may be steered to be biased against one or the other of the side walls. In each case, electrical energy is usually applied to the prior art racing cars through which electrically conductive strips extending along the track. Such an arrangement, however, has limitations, since it is essential that the cars be maintained in electrical contact with their electrically conductive energizing strips.
Copending Application Ser. No. 136,259 filed in the name of Richard L. May on July 31, 1980 (now abandoned) describes an electrically energized toy racing car which uses two separate motors to drive the two front wheels of the car so as to enable the car to be steered by independently varying the speeds of the two motors, and to be driven at various speeds, by concurrently varying the speeds of the two motors. An objective of the present invention is to provide a remote control system for a toy racing car of the type discussed in the copending application, and which does not require electrically energized strips, so that each car may be steered and driven along the track at different controlled speeds without the necessity for maintaining the car in electrical contact with the energizing strips used in the prior art arrangements.
In the embodiment of the invention to be described, a pulse code is used with several variations, as will be described. Analog control signals from the individual manually controlled controllers are transformed into binary coded digital words of a selected length, which length can be changed depending upon the application. In a typical installation, each word contains four commands for each car and may, for example, contain a total of eight commands for independently controlling two cars.
Each car in the embodiment to be described is equipped with a first electric motor which controls one front wheel and a second electric motor which controls the other front wheel, as described in the copending application referred to above. The four commands for each car are "forward right motor", "reverse right motor", "forward left motor", and "reverse left motor". Such commands are all that are necessary in order to drive the car forward or reverse at varying controlled speeds, and to steer the car. Each command is represented by a binary digit which causes the designated motor to become energized when the corresponding bit is a "1", and which causes the designated motor to become de-energized when the corresponding bit is a "0".
Steering is accomplished by causing the motors to be energized and de-energized at different rates as successive bits are controlled to be "1's" or "0's" in successive words of the control signal; and speed control is achieved by controlling the rate at which the motors are energized by energizing and de-energizing both motors at the same rate but by varying the rate by varying the number of "1's" and "0's" in successive words of the control signal. It is clear that as successive words of the control signal includes fewer and fewer "1's", the motors will be driven at slower and slower speeds.
In the system to be described, a binary "0" is detected by the receiver by the receipt of 2-5 successive pulses in a particular bit with no more than two successive pulses missing; and a binary "1" is detected by the receipt of 6-13 successive pulses in a particular bit with no more than two successive pulses missing. Each word of the control signal is preceded by a synchronizing bit which is detected by the receipt of 14, or more, successive pulses with no more than two successive pulses missing. Such a format renders the system of the invention virtually immune from noise interference, and obviates the need for external adjustments at the transmitter or receiver, and usual component tolerances can be used. All timing within the system of the invention is based on a reference clock signal which may have a frequency, for example, of 50 KHz. The system to be described has a 16 bit resolution/channel, and a 10 Hz up-date (refresh cycle).
A feature of the embodiment of the invention to be described is the manner in which identical transmitters can be hooked together to double the number of cars which can be independently controlled.
The complexity of the encoder integrated circuit in the transmitter of the system is due largely to the logic required to convert the analog inputs from the controllers into appropriate digital control signals. Accordingly, for most purposes, two-car control systems are appropriate. Then, if more than two cars are to be controlled, a second identical transmitter may be connected to the first transmitter and its integrated circuit used to convert the analog signals from two additional controllers into the digital control signals, with the first integrated circuit being used to separate the digital control signals from its two controllers and the digital control signals from the additional two controllers into four distinct control channels for operating four separate cars. This approach is more advantageous than building the capability of responding to four controllers for controlling four separate cars into the original integrated circuit with the resulting added complexity and cost, where under most circumstances, the provision of two controllers to control two cars is sufficient.
Specifically, the analog-digital control logic in each integrated circuit in each transmitter has the ability to convert the analog control signals from its two controllers into the first eight bits of a 16 bit word and also into the last eight bits of the 16 bit word. However, the remaining circuitry in the integrated circuit transmits only the first eight bits over two of the four allocated channels to the receivers in the two controlled cars, the remaining eight bits being transmitted in the other two channels as "0's". However, if two transmitters are connected together, the circuitry in the integrated circuit of the first transmitter will respond to the last eight bits of each 16 bit word from the analog-digital conversion logic of the second transmitter to transmit control signals from two additional controllers for an additional two cars in the other two channels.
Therefore, in the embodiment of the invention to be described, two independent systems can be combined with no additional hardware, using the components of each, to double the number of cars that may be controlled.
It should be understood that although the control system of the invention will be described in conjunction with the capacitive control of toy racing cars, the control system has wide applications in the transmission of commands to one or more controlled instrumentalities, of any appropriate type, with a high degree of noise immunity. The system of the invention may also be adapted to ultrasonic, infrared, and other types of energy. Also, the system of the invention is compatible with radio frequency control system since, if so desired, the transmitter outputs may be modulated on radio frequency carriers and transmitted by a radio link.